Some internal combustion engines employ a gasoline particulate filter (GPF) in an exhaust system to trap particulate matter flowing through the exhaust system and thereby meet emission standards. GPFs may be constructed of porous ceramics, or other porous materials. Regardless of the specifics of the design, the purpose of the filter is to filter soot particles, the soot particles consisting of solid carbon often with adsorbed hydrocarbons, out of exhaust gas flowing through the filter and then hold the filtered soot particles within the filter until the filter is regenerated by combusting soot to form gaseous products. Soot is produced in a gasoline engine primarily in the first few minutes following cold start. In addition to soot, the exhaust gas also carries incombustible solid material, which may be referred to as ash, which may also be trapped by the GPF. However, since the ash is incombustible, it may remain in the filter for its useful life. Ash is derived primarily from lubricating oil entering the combustion chamber or exhaust ports. Other sources include corrosion from the exhaust manifold and debris from the upstream catalytic converter. Ash is produced during all engine operating modes. As particulate matter (e.g., ash and soot) accumulates in a particulate filter (e.g., the GPF), exhaust backpressure may increase, which can adversely affect fuel economy. While actively regenerating the GPF may remove the stored soot, the stored ash may remain within the filter after regeneration, and thus the exhaust backpressure created by the GPF may only partially be reduced. As such, the ash may continue to contribute to the exhaust backpressure on the engine, thereby reducing engine torque output and/or engine fuel economy.
Other attempts to address particulate matter build-up within a GPF include employing a bypass system that bypasses exhaust flow around the GPF. Specifically, the bypass system may include a bypass passage in parallel with the GPF and a valve disposed within the bypass passage for controlling flow through the bypass passage. One example approach is shown by Gonze et al. in U.S. Patent Application No. 2012/0060482. Therein, Gonze discloses methods of regenerating a gasoline particulate filter (GPF) in a spark-ignition engine. Gonze also discloses a GPF bypass apparatus for the GPF wherein an annular channel extends through the central axis of the GPF. The portion of the annular channel which is closest to the upstream catalytic converter (i.e., where exhaust first comes into contact with the GPF and channel) is outfitted with an operable valve to direct exhaust gasses during various operating conditions of the vehicle.
Another example approach is shown by Kono et al in U.S. Pat. No. 4,974,414 and Arai et al in U.S. Pat. No. 5,105,619 which also disclose methods and systems for regenerating a particulate filter in a spark-ignition engine. Both references employ a bypass passage around a GPF, the bypass passage including a valve with a portion of the valve arranged external to the bypass passage. The bypass passage runs parallel to and outside of the GPF, adjacent to the GPF.
However, the inventors herein have recognized potential issues with such systems. As one example, the valve situated at the mouth of the annular passage (e.g., within the GPF enclosure, as shown in Gonze) makes access to said valve for repair/replacement difficult, and traps heat within the system, posing a challenge to component durability. As another example, bypass passages located adjacent and parallel to the GPF enclosure increase the diameter and/or width of the system, thereby increasing the total packaging space of the GPF system and emission control devices.
As one example, the issues described above may be addressed by an apparatus including a gasoline particulate filter (GPF) arranged in an exhaust passage, a central bypass passage including a first portion disposed upstream of the GPF and a second portion passing through a center of the GPF, a converging cone forming a portion of the exhaust passage and arranged upstream of and connecting to the first portion, one or more outer passages coupled between the converging cone and the GPF and spaced away from the central bypass passage, and a valve arranged within the first portion. In this way, packing size of an exhaust system including the GPF may be reduced and the valve in the central bypass passage may be more easily accessed for repair and/or replacement.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.